The present invention relates to a test method and apparatus and more particularly to a test method and apparatus for accelerated reliability testing.
The use of high temperatures and low temperatures as a means to stress electrical and electronic components in order to uncover weaknesses and faults without damaging healthy components is well known. Military standard Mil-Std-785B, Task 301 addresses the use of environmental stress as a method of inducing early failures due to part weaknesses and workmanship defects.
U.S. Pat. No. 3,710,251 issued to Holderfield et al. discloses a fixture for holding an unmounted microelectronic die or wafer and subjecting the microelectronic die or wafer to hot and cold temperatures while performing circuit tests. The hot and cold temperatures are derived from hot and cold liquids respectively and transferred through the holding fixture to the die or wafer. At column 2, lines 29-33 mention that rapid cycling between high and low temperatures is possible if such is required for circuit testing.
U.S. Pat. No. 4,870,355 issued to Kufis et al. discloses a fixture for holding a die or wafer and directly heating or cooling the die or wafer with hot or cold nitrogen gas.
U.S. Pat. No. 4,962,355 issued to Holderfield et al. discloses a fixture for heating or cooling a single electronic device, such as a hybrid semiconductor chip, with an unspecified fluid.
U.S. Pat. No. 4,945,302 issued to Janum discloses a test circuit board for mounting a plurality of microelectronic circuit and then subjecting part of the test circuit board and the microelectronic circuits thereon to elevated temperatures as a burn in procedure. The other part of the circuit board has test support circuits thereon and is not subjected to the elevated temperatures.
These patents all have the short coming that they do not disclose a method or an apparatus for testing a production printed circuit board (PCB), or a PCB assembly that has many electrical and electronic components attached thereto and inter-connected thereby. Yet each PCB assembly represents a considerable investment by the manufacturer, so it is desirable to uncover and repair any fault or weakness on each PCB and on each PCB assembly.
Thus, it is an object of the present invention to provide a test apparatus for mounting a PCB or PCB assembly, testing the operation of the PCB assembly during rapid temperature cycling of the entire circuit board and all the electrical and electronic components thereon.
It is another object of the present invention to provide a test method for testing a PCB or a PCB assembly during rapid temperature cycling in order to uncover weaknesses and faults thereof.